High powered 3/8" or 1/2" variable speed reversible (VSR) drill
If on a budget we recommend a corded Dewalt 1/2" VSR drill.
Otherwise we use and recommend the cordless Milwaukee M18 1/2" hammer drill, especially one from the M18 FUEL line with brushless motors (shown in picture) - likely the last drill you'll ever buy. With two speed settings, the slow speed is perfect for milling grain with the trigger fully depressed. The high speed is perfect for wort aeration.
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